ADO: 1.It is a COM based library. 2.Classic ADO requires active connection with the data store. 3.Locking feature is available. 4.Data is stored in binary format. 5.XML integration is not possible. 6.It uses the object named Recordset to reference data from the data store. 7.Using Classic ADO, we can obtain information from one table or set of tables through join. We cannot fetch records from multiple tables independently. 8.Firewall might prevent execution of Classic ADO. 9.Classic ADO architecture includes client side cursor and server side cursor. 10.We cannot send multiple transactions using a single connection instance. ADO.NET: 1.It is a CLR based library. 2.ADO.NET architecture works while the data store is disconnected. 3.Locking feature is not available. 4.Data is stored in XML. 5.XML integration is possible. 6.It uses Dataset Object for data access and representation. 7.Dataset object of ADO.NET includes collection of DataTables wherein each DataTable will contain records fetched from a particular table. Hence multiple table records are maintained independently. 8.ADO.NET has firewall proof and its execution will never be interrupted. 9.ADO.NET architecture doesn't include such cursors. 10.We can send multiple transactions using a single connection instance.
ADO stands for ActiveX Data Objects, were a COM Library, OLE DB, mainly used in Visual Studio 98. ADO.NET is the evolution to work with Microsoft (Dot).NET Framework. Only if you are writing old aplications with COM (Common Object Model) you will use ADO. If you are using Visual Studio 2k, there is no why to not use ADO.NET.
in a simple term or lay mans language Ado.net is just the integration of your Database with your project which you develop in either vb.net or C#. i.e integrating your sqlserver to your visual studio project.
ADO.NET is stateless mechanism. I can treat the ADO.Net as a separate in-memory database where in I can use relationships between the tables and select insert and updates to the database. I can update the actual database as a batch